Process for removing nitrogen



United States Patent 3,193,496 PROCESS FOR REMOVING NITROGEN 'Guenther K. Hartung, Pittsburgh, Pa., assignor to Gulf Research 8; Development Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Filed Dec. 6, 1961, Ser. No. 57,545 16 Claims. (Ci. 2ll8212) This invention relates to the removal of nitrogen-containing compounds from petroleum fractions.

It has been found that nitrogen-containing compounds are deleterious in certain refining processes because of their poisonous effect on catalysts. 'It' is also speculated that nitrogen-containing compounds, contribute to discoloration, formation of sludges and gum and general instability of petroleum products. It is, therefore, highly desirable to develop effective means for the removal of these nitrogen-containing compounds. In general, nitrogen-containing compounds are classified as basic and non-basic types, The basic type canusually be removed by a simple acid washing, but the removal of the non-basic types presents a more difficult problem. Both the basic and non-basic nitrogen-containing compounds can be removed by the method of the present invention.

In accordance with the invention, the nitrogen content of a nitrogen-containing petroleum fraction is reduced by a process comprising contacting said nitrogen-contain ig petroleum fraction with a mixture of heavy metal salts selected from the group consisting of iron salts and zinc salts. The unreacted salts and metal salt complexes, formed by the reaction of the metal salts and the nitrogencontaining compounds, are thereafter separated from the petroleum fraction. In one preferred embodiment of the invention, the basic nitrogen-containing compounds are selectively removed before treatment of the petroleum fraction with a mixture of heavy metal salts. In another preferred embodiment of this invention, the olefin and sulfur contents of the nitrogen-containing petroleum fraction are reduced before treatment with the heavy metal salts. In yet another preferred embodiment of this invention, the heavy metal salts and metal salt complexes, which are separated from the treated oil, are regenerated for reuse.

The charge stocks for this process comprise any nitrogen-containing petroleum fraction. By nitrogen-containing petroleum fraction. is meant. any petroleum, fraction comprising nitrogen-containing compounds in admixture with other compounds and hydrocarbons. In particular, the charge stock may comprise any nitrogen-containing petroleum fractionv boiling between. about 40. C. and 550 C. or higher at atmospheric pressure. For example, naphthas, furnace oils, gas oils, full range crudes, lubricating oils, or residuums, may be employed. Nitrogencontaining petroleum fractions boiling between 200 C. to 400 C., i.e., furnace oils and gas oils are preferred charge stocks for the process of this invention since the method of this invention is particularly applicable to stabilizing such charge stocks against, for example, gum formation,

and also for preparing such charge stocks for further catalytic treatment as noted above. The charge stocks for this process may also comprise some sulfur-containing compounds. 'The preferred charge stock for the process of this invention is one of low sulfur content. The sulfur content of the charge stock may be lowered by any suitable means. One preferred means, for example, is by a mild hydrogenation.

The nitrogen content of a nitrogen-containing petroleum fraction may be reduced by contacting the nitrogencontaining petroleum fraction with selected heavy metal salts. It has now been found that a mixture of heavy metal salts selected from the group consisting of iron salts and zinc salts has a synergistic eflfect in removing nitrogen-containing compounds from a nitrogen-containing petroleum fraction. By iron salts is meant any compound of iron with a negative organic or inorganic radical. By ,zinc salts is meant any compound of zinc with a negative organic or inorganic radical. Suitable organic sails of iron and zinc include, for example, the formates, acetates, and propionates. Suitable inorganic salts of iron andzinc include, for example, the sulfates, nitrates,

phosphates and halides, such as, the chlorides. The in- ,Zinc chloride may suitably be formed by direct reaction.

of zinc or. zinc oxide with aqueous hydrochloric acid.

Any suitable means maybe .employedfor contacting the heavy metal. salts .and the nitrogen-containing charge stock. For example, the charge stock may be passed through a column packed with thesalts, or the salts may be slurried with the charge stock and thereafter separated. The treated charge stock and salts may be separated by any. suitable means, for example, by filtration, centrifugation or decanting. It is preferred that .the charge stock be in the liquid phase'for improved contacting with the heavymetal salts. In addition, if desired, the more viscous type charge stocks maybe di- :luted with an inert solvent, such as, a low boiling saturated aliphatic .hydrocarbomfor example,isohexane, to

att red. sea ed. ime

improve contacting between the salts and the charge stock.

Th em r tur .o sqnta tinemevb between C. to 200 C. or higher. In general,;roorntemperature is preferred, although ingreasedtemp'eratures -may aid p omo n s t ple i nn s nd hu redu the The lower temperature which may be employed is limited by the solidification point of the charge stock. The upper temperature which may be employedislimited bythe thermal decomposition of the rnetal salt complexes, and the promotion of undesirable sidereactions between the metal salts and other components of the charge stoclgsuch as, the halogena- -tion of aromatic compounds if a halogen salt is employed.

creased by improved contacting between the metal salts and the nitrogen-containing compounds, 'such as, by increased agitation or, mixing, and by increasing the temperature of contacting as noted above. Contact times of at least about two minutes may'be employed with preferred contact times between minutes and four hours. j

The molar ratio of zinc to iron may be from 1:10 to 10:1 with preferred molar ratios from 1:1 to 2:1. The amount of heavy metalsalt mixture to be employed is a function of the amount of nitrogen in the charge stock. In general, the molar ratio of salt mixture to nitrogen, calculated as the monoatom, in the charge should be at least 1:1, with preferred molar ratios between 60:1 and 200:1. Additional amounts of salt mixture will be required if other components, such as certain sulfur and oxygen compounds, are present in the charge stock which end to react with the heavy metal salts.

The separated metal salt complexes may then be regenerated in any suitable manner. 'By regeneration is meant the recovery of the heavy metal salts from the metal salt complexes. Regeneration usually involves ."decomposition of the complexes into a metal-containing portion and a nitrog'enicontaining compound portion followed, if required, by a conversion of the metal-containing portion to the desired metal salt. Before regeneration it may be desirable to wash the salts with a suitable solvent, such as a low molecularweight aliphatic hydro amounts of treated charge stock physically adhering to the salts.

One preferred inert gas, such as nitrogen. The nitrogen-containing compounds may be removed from the decomposition 4 furnace oil by slurrying and shaking for three hours at room temperature and atmospheric pressure.

In the second set of experiments, the procedure of the first set was repeated except in the second set 10 milliliters of water were added to each oil plus salt mixture.

In the third set of experiments, 250 milliliters of the hydrogenated furnace oil were passed by gravity at atcarbon, such as isohexane, to remove any residual method of regeneration involves thermally decomposing the metal salt complexes at temperatures between 250 C. and 600 C-in thepresenceof an.

zone by any suitable means, such as by an inert sweep' gas, such as nitrogen, and thereaft'er condensed. The

metal-containing portion may, in some cases, be im-,

mediately ready for reuse while inother cases further processing may be required. 7

'Another preferred method of regeneration is the oxidative regeneration of the metal salt complexes to form metal oxides and combustion products of the organic material. Themetal oxides may then be converted to the desired metal salts by reaction of the metal oxides.

'in Table II below.

mospheric pressure through an adsorption column (100 centimeters X 25 centimeters diameter) packed with a dry mixture of sand and salt in a 4:1 weight ratio of sand to salt. a V

All of the treated portions of the oil, including those from the adsorption column, were analyzed for nitrogen content. The results of all of these experiments are shown A comparison of the results from all three sets of experiments shows that only the zinc and iron salts were even partially effective for lowering the nitrogen content of -thecharg e stock. The addition of water or sand to the salts appeared to lessen the effect of the salts and are,

therefore, not preferred diluents. The

salt used in Example -6 in Table II is the so-called Reineke salt which is used in analytical work for the complexing and identification of nitrogen-contaning compounds, as described, for example, in an article entitled Colorimetric Determination of Nitrogenous Substances in Complex I Mixtures as Reineckatesfby Masse in Pharmaceutica with the appropriate reactant in any manner well known 7 in the 'art.

The invention will be further described with reference.

to the following specific examples. The charge stock I TABLE I I Gravity, API 25.7 Boiling range, C.:

V 10% point 246 point 280 point 316 I End point 339 FIA (ASTM D1319):

Aromatics, volume percent 60.4 Olefins, volume percent 1.9 'Saturates, volume percent 37.7 Total nitrogen, p.p.m. Basic nitrogen, p.'p.m. ..e a; 25, Sulfur, weight percent 1;, 0.09 7

Three sets of experiments were performed to evaluate the effectiveness of various metal salts for removing the nitrogen-containing compounds from the, hydrogenated furnace--oil. In the first setofexperiments, 25 grams of each of the salts listed in Tablell below were separately contacted with 250 milliliter portions of the hydrogenated Acta I-Ielvetica, vol. 33, p. 880 (1958). The fact that this Reineke salt was not effective for nitrogen removal makes the results with the iron and Zinc salts of this invention even more unexpected. a

A series of experiments was then run to determine the effectiveness of a combination of salts for the removal of nitrogen-containing compounds. The results of these experiments are shown in Table III below. Again, 25 grams of each salt were contacted with 250 milliliter portions of the hydrogenated furnace oil by slurrying and shaking'for three hours at room temperature and atmospheric pressure.

' TABLE 111 Example Nitrogen, Number p.p.m.

newe

. The hydrated forms of the iron, copper, and cobalt salts were used as in Table II above.

The experiments in Table III showthat mixtures'of iron and zinc salts are unexpectedly superior in nitrogen-re- 70.

'5 these experiments 250 milliliters of the charge oil were admixed with varying amounts of a mixture of iron and zinc chlorides wherein the molar ratio of iron to zinc was 1.98:1. The results of these are shown in Table IV below.

A comparison of Examples 12 through 18 on Table IV shows that, in general, an increasing salt concentration results in the formation ofproducts with a lower nitrogen content.

Comparing Example 12 with Examples 1 and 2 shows the synergistic effect of a mixture of iron and zinc salts; for the use of grams of the mixture of salts in Exampic 12 resulted in a far greater reduction in nitrogen content than grams of either salt alone as in Examples 1 and 2.

In the following tour examples the charge stock was a hydrogenated furnace oil from which the basic nitrogencontaining compounds were removed by washing with hydrochloric acid (1 N). The properties .of this Charge stock are the same as those in Table I above, except the total nitrogen is 120 parts per million and the basic nitrogen is essentially zer-o parts per million.

Example 19 Five hundred milliliters of the charge oil were slurried with 50 grams of ferric chloride at room temperature and atmospheric pressure for three hours in a closed system. The precipitates were removed from the oil by filtration, .and'the oil was Washed with water repeatedly to remove entrained salts, and finally dried. A portion (450 grams) of the resultant oil was then treated with 50 grams of zinc chloride; the precipitates weresseparated as above; and the oil washed with water and dried. The resultant oil contained 28.parts1per million ofnitrogen.

Example 20 Example 19 was repeated except the oil was treated first with ,the zinc chloride, and then with the ferric chloride. After the initial zinc chloride treatment the oil contained 110 partsper million of nitrogen, while after treatment with both salts individually the oil contained 28 parts per million of nitrogen.

The results of Examples 19 and 20 indicate the sequence of treatment with the iron and'zinc salts individually is not critical with respect to the finalnitrogen content.

Example 21 Example 22 Example 21 was repeated except the sequence of the individual salt addition was as in Example 20. The nitrogen content of the products from successive treatments with 100 gram portions of zinc chloride and ferric chlo- 6 ride, .and then a mixture of 20 grams of zinc chloride and 20 grams of ferric chloride was 110 parts per million, 19.3 parts per million, and 2.4 parts per million respectively.

A co-mparison of Examples 21 and 22 shows again that the sequence of salt addition is not critical with respect to the final nitrogen content.

A comparison of Examples 19 and 21 shows the syn ergistic effect in using a mixture of iron and zinc chlorides. In Example 19, 100 total grams of separate 50 gram portions of the two salts lowered the nitrogen content of the oil to 28 parts per million. In Example 21, 200 total grams of the separate salts lowered the nitrogen content of the oil to only 25 parts per million. An additional treatment with only 40 grams of a 1:1 weight mixture f the salts unexpectedly reduced the nitrogen level to 2.5 parts per mil-lion. These same conclusions can be drawn by a comparison of Examples 20 and 22.

Example 23 In this example, 250 milliliters of a crude gas ,oil, whose analysis is given in TableVI below, were slurried with a mixture of 25 grams of ferric chloride and 25 grams of zinc chloride at room temperature with constant agitation for three hours.

TABLE Y1 Gravity, API 32.5

Boiling range, C.:

' 10% point 277 50% point 338 %.point 386 End point 404 Total nitrogen, ppm 380 Basic nitrogen, ppm. 126

Sulfur, weight percent 0.86

After treatment, the crude gas oil was filtered and water washed to remove final traces of the salt. Analysis of the treated gas oil showed the nitrogen content had been decreased from the original 380 parts per million to 7.3 parts per million.

The metal salt complexes were considered freed of entrained oil after repeatedly pulverizing the metal salt complexes to reducethe particle size of the complexes followed by repeated washings of the complexes with isohexane.

It was also found that regeneration of the metal salt complexes could be efiected by thermal decomposition.

As an example of this, a three gram portion of the pulverized and washed metal salt complexes was heated in a ,tubeat the rate 7 to 8 C. per minute until a temperature of 450 C. was reached. A stream of nitrogen was continuously passed through the tube to remove any volatilized material. The volatilized material was thereafter condensed and found to have a nitrogen content of 1.09 percent.

A mixture of metal salt complexes, wherein the weight ratio of iron chloride to zinc chloride was 1: 1, was also regenerated by heating the complexes in an open crucible to combust the organic material and form metallic oxides. Due to the volatility of the zinc chloride, a portion of the zinc was probably lost to the atmosphere. Suitable apparatus could easily be installed, of course, to limit any loss of metallic compounds during regeneration.

' The remaining metallic oxides were dissolved in boiling 4 N hydrochloric acid; the water thereafter removed on a steam bath, and the corresponding chlorides dried in an oven maintained at 90 C. until dry enough to be pulverized.

A portion of a 1:1 weight mixture of iron and zinc chlorides, which had been used to remove nitrogen-containing compounds from a hydrogenated furnace oil, was regenerated by oxidation and reformation of the chlorides as described above, and the mixture of regenerated salts was tested for activity in the following manner.

was stirred for threehours at room temperature.

Example 24 Sixteen grams of the regenerated salt mixture were slurried with 80 milliliters of the hydrogenated furnace oil whose analysis is given in Table I above. The mixture nitrogen content of the product was 26 parts per million showing that the regenerated salts can be reused.

Example 25 Example 24 was repeated except eight grams of zinc chloride were added to the 16 grams of regenerated salt mixture'and 120 grams of oil'were used to maintain the 7 same salt to oil ratio- The nitrogen content of the prod- The As also noted above, the sulfur content ofthe'charge stock may be lowered by any suitable means, such'as,

by a mild hydrogenation. By a mild hydrogenation is meant hydrogenation conditions whereby the olefin'and sulfur contents of the charge stock are reduced'while effecting little or no hydrogenation of the aromatic constituents.

Resort may be had to such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

I claim:

1. A process for reducing the nitrogen content of a nitrogen-containingv petroleum fraction which comprises contacting said nitrogen-containing petroleum fraction with a mixture of at least one iron halide and at least one zinc halide.

2. A process for reducing the nitrogen content of a V nitrogen-containing petroleum fraction boiling between 40 C. and 550 C. which comprises contacting said A nitrogen-containing petroleum fraction in the liquid phase at a temperature between 50 C. and 200 C. with a mixture of at least one iron halide and at least one zinc halide. a

3. A process according to claim'Z wherein the molar ratio of iron to zinc in the mixture of halides is between 1:10 and :1. 7

4. A process according to claim 3 wherein the molar ratio of metals in the mixture of halides to nitrogen in the nitrogen-containing petroleum fraction is at least l:l.

5. A process for reducing the nitrogen content. of a nitrogen-containing petroleum fraction boiling between 40 C. and 550 C. which comprises contacting said nitrogen-containing petroleum fraction in the liquid phase a at a temperature between '50 C. and 200 C. with a 7 mixture of iron chloride and zinc chloride.

7. A process according to claim 6 wherein the nitrogencontaining petroleum fraction boils between 200 C. and 400 C. V

8. A process according to claim 6 wherein the molar ratio of iron to zinc in the mixture of metal chlorides is between 1:10 and 10:1.

9. A process according to claim 8' wherein the molar ratio of metals in the mixture of metal halide to nitrogen and nitrogen-containing petroleum fraction is at least 1:1.

10. A process for reducing the introgen content of a nitrogen-containing petroleum fraction comprising basic and non-basic introgen-containing compounds which comprises treating said nitrogen-containing petroleum fraction to selectively remove the basic nitrogen-containing compounds, and thereafter contacting the treated nitrogen-containing petroleum fraction with a mixture of at least one iron halide and at least one zinc halide.

11. A process according to claim 10 wherein the iron halide is ferric cholride and the zinc halide is zinc cholride. 12. A process for treating a nitrogen-containing petroleum fraction comprising sulfur, olefins and nitrogen-containing compounds which comprises subjecting said nitrogen-containing petroleum fraction to hydrogenation to reduce. the sulfur and olefin content thereof and thereafter contacting the hydrogenated petroleum fraction with a mixture of at least one iron halide and at least one zinc halide to reduce the introgencontent of the hydrogenated petroleum fraction. I

13. A process according to claim 12 wherein the iron halide is ferric chloride and the zinc halide is zinc chloride;

zinc halides and the introgen compounds present in the nitrogen-containing petroleum fraction; thereafter regenerating said metal salt complexes; and thereafter recycling said regenerated metal salts.

15. A process according to claim 14 wherein the iron halide is ferric chloride and the zinc halide is zinc chloride.

200 C., and 400 C. which comprises contacting said nitrogen-containing petroleum fraction in the liquid phase at a temperature between C. and 200 C. with a mixture of at least one iron halide and at least one zinc halide. g

6. A process for reducing the nitrogen content of a nitrogen-containing petroleum fraction boiling between 16. A process forrcd-ucingthe nitrogen content of a nitrogen-containing petroleum fraction which comprises contacting said nitrogen-containing petroleum fraction with a mixture of ferric chloride and zinc chloride.

ALPI- IONSO D. SULLIVAN, Primary Examiner. 

1. A PROCESS FOR REDUCING THE NITROGEN CONTENT OF A NITROGEN-CONTAINING PETROLEUM FRACTION WHICH COMPRISES CONTACTING SAID NITROGEN-CONTAINING PETROLEUM FRACTION WITH A MIXTURE OF AT LEAST ONE IRON HALIDE AND AT LEAST ONE ZINC HALIDE. 